Integrated Regional Water Management Plan

Water Management Implications of Restoring Meso-scale Watershed Features

Title

Water Management Implications of Restoring Meso-scale Watershed Features

Abstract

Stream channels with adjustable bed and banks have been proven to develop predictable features of pattern, form and profile centered around the dynamic equilibrium of available sediment and available discharge. Drainage basins of all sizes develop equivalent features that provide the same functions at the basin scale. The mountainous, western United States has historically been a region where water, its location, quantity and time of availability, has determined the character of settlement and growth. A region with distinct wet and dry seasons, this landscape has fluvially-evolved landscape features that buffer the effects of hydrologic extremes on the ecosystems of the region. The origin of much of this water is the rainfall and snowpack of the numerous mountain ranges, extending from the Sierra Nevada and Cascade Mountain chain eastward through the Great Basin ranges in Nevada to the Rocky Mountains. These water- producing areas are often hundreds of miles from the urban and agricultural consumers, resulting in the development of some of the most complex water detention and conveyance systems in the world. Concurrent with this extensive water development, a little recognized but increasingly important phenomenon has occurred; the entrenchment of stream channels in the alluvial fans, meadows and valleys of the watersheds. Channel entrenchment disconnected streams from naturally developed floodplains and subsurface reservoirs, reducing the sediment and water storage capacity of the landscape.

Purpose

To understand the importance of restoring the meso-watershed functions in improving water quality, timing of flows, sediment reduction, and aquatic and riparian habitat. Quantitative data and qualitative observations from a number of watershed projects undertaken in the Feather River watershed illustrate these concepts.